 Instead, terranes and the accretionary wedge have been uplifted to form a series of coast ranges and exotic mountains.A high rate of sedimentation from the outflow of the three major rivers (Fraser River, Columbia River, and Klamath River) which cross the Cascade Range contributes to further obscuring the presence of a trench.However, in common with most other subduction zones, the outer margin is slowly being compressed, similar to a giant spring.